What is a common source of sulfur trioxide in clinker? How can it occur as in the clinker?
Coal used in the kiln
occurs as impurity oxide or free salt
What is a common source of sulfur trioxide in cement? How can it occur as in the cement?
Source is intentional addition of gypsum,hemihydrate, or anhydrate to control setting
Which compounds often result in the formation of ettringite?
Gypsum and sulfates
Write the chemical reaction that results in ettringite and ettringite’s shorthand.
C3A+H+S(with line) -> C6AS(with line)3H32
At what stage can ettringite formation become problematic?
During the plastic stage is fine, but if in the hardened stage it can become unsound
Explain the simplified form of external sulfate attack.
monosulfoaluminate + sulfate -> ettringite.
What concrete performance characteristic is affected by the sulfate aluminate balance?
Durability
How does ASTM set sulfate limits in context of external sulfate attack?
The limit depends on the C3A content.
Which properties can be affected by gypsum content in concrete?
Setting, drying shrinkage, strength development, and durability
IN what form do alkali oxides form in cement?
Free alkalis (alkali sulfates) or impurity oxides in the crystal structure
What is the problem with having alkali oxides in cement mix?
alkalis attack particles of reactive silica in aggregates creating unsoundness
What is the maximum alkali content set by the ASTM?
0.6%
What is the source of alkali that leads to a potential alkali silica reaction (ASR)?
Raw feed, coal
List properties of this portland cement main compound in terms of strength and heat liberation: Tricalcium silicate
Concrete early strength, moderate heat liberation but high contribution
List properties of this portland cement main compound in terms of strength and heat liberation: Dicalcium silicate
Concrete later strength (7+ days), low heat liberation and low heat of hydration
List properties of this portland cement main compound in terms of strength and heat liberation: Tricalcium aluminate
high reaction rate, very high heat liberation and very high heat of hydration
List properties of this portland cement main compound in terms of strength and heat liberation: Tetracalcium aluminoferrite
moderate reaction rate, moderate heat liberation and moderate heat of hydration
What do A and MH stand for in concrete type names?
Air entrainment and Moderate heat
